This invention relates, generally, to sewage water pumping stations, and tanks therefor, and in particular to improvements thereof for inhibiting clogging of the pump by sludge banks and/or solid bodies.
Pumping stations of the type with which this invention is concerned are provided with one or more inlets for the sewage water and normally one outlet pipe, the latter being in communication with the pump outlet or discharge. An example of such is disclosed in Swedish Patent No. 366,013, and its corresponding U.S. Pat. No. 3,957,633, issued on May 18, 1976, to Giuliano Gatti, et al, for a Sewage Treatment Method and Apparatus.
In typical prior art, a submersible pump unit, comprising the sewage water pump, is normally lowered into the sewage water, confined within the pumping station tank, along guides. It is so arranged that the pump unit, in its fully lowered position, aligns its outlet with the outlet pipe within the station tank. The pump unit must seal against the outlet pipe of the station tank without any bolting or fasteners of any kind. For this purpose, a so-called connection support is arranged at the bottom of the station tank, and is provided with a pipe part, attached to the outlet pipe at one end, and having a flange at the opposite end. A corresponding flange on the pump contactingly aligns with the connection support flange. Lowermost ends of the guides are coupled to the connection support.
Sewage water contains a lot of solid bodies, such as sludge, which are readily agglomerated on the tank bottom as sludge banks, rags and other, elongated objects. Such may wind around the pump unit and its connecting parts. Too, sludge banks and rags are a hindrance to the circulation within the tank, and my also clog the pump inlet.
It is a known practice, to solve the problem with the sludge banks in the tank, by means of intermittingly-operating, mixing devices of the type shown in the Swedish Patent No. 8900 597-9, and its corresponding U.S. Pat. No. 4,948,342. Another method, drawn to the same purpose, is to install machines or devices which keep the sewage water moving within the tank.
Yet another method which is used to prevent sludge from collecting at the bottom of the tank is to design the bottom with steep slopes, and then arrange the pump inlet at the lowest point in the tank. However, even here, there remains the problem that elongated objects stick to the guides, the connection supports for the pump, and related, pump unit connecting parts.